How do earthworms spread?

There are no native earthworms in most of Canada and the northern United States because they were wiped out during the last ice age (11 000 years ago).

European earthworms were likely introduced to North America when settlers brought plants and soil from Europe which contained earthworms or their cocoons (egg cases)

They may also have been introduced by ships that used soil as ballast, which was dumped on shore to adjust the weight of the ship

Similarly to ballast water, which is often contaminated with aquatic invasive species, soil used for ballast probably contained earthworms or cocoons

Due to these activities, earthworms have been found around human settlements in North America since the late 1800s

More recently, earthworms from Asia have been found in North America but have not yet been reported in Alberta

Figure A: Lumbricus terrestris cocoon, produced when two Lumbricus earthworms mate. Figure B: Dendrobaena octaedra cocoon - this species reproduces asexually so one individual can produce a cocoon. The developing earthworm is visible inside

Spread within Alberta

There are at least 14 species of non-native earthworms in Alberta

They are present in cities and towns but have not yet spread into some remote areas

Scientists first began noticing earthworms in forests in the foothills of Alberta in the mid-1980s

Our research in the boreal forest of northern Alberta suggests that they may have been present in some areas since the 1950s, while other areas have either recently been invaded or have no earthworms present

Earthworms are estimated to spread only 5 to 10 meters per year on their own

Because of this slow rate of spread, human activities are extremely important for earthworm spread

Earthworms can be introduced to forests by anglers dumping their leftover bait on land or in the water

Vehicles can transport earthworms or cocoons in their tire treads

Earthworms and cocoons may also be transported along streams

Native Earthworms

Some areas of North America that were not glaciated have native earthworms

In Alberta, one native species has been found in the Porcupine Hills, an area that was not covered by glaciers

Our Worm Tracker app for data collection is available on iTunes.

How To Help

Worm Invasion Poster

ABOUT Alberta Worm Invasion Project

The Alberta Worm Invasion Project's objective is to increase public awareness of earthworm invasions. We are conducting research at the University of Alberta on earthworm spread and impacts in Alberta's forests. For more information, please contact us.